Multiplex signaling system



Feb. 9 H. A. AFFEL MULTI FLEX S IGNALNG SYSTEM 4000- v j z9000- H. A. AFFEL MULTIPLEX SIGNALING SYSTEM Filed May 24, 1920 2 Sheets-Sheet 2 Patented Feb. 9, 1.926.

' UNITED vs i'arlazsi ra'riiNrl oFrICi-z.

HERMAN A. ArFEL, or' BROOKLYN, NEW YORK, iissIGNoR- 'ro AMERICAN-TELEPHONE?.-

AND TELEGRAPH -COMPANSL A CORPORATION OF NEW YORK.

i NUL'rIrLEX siGNAL'ING SYSTEM.

Application led May 24,

[oV all whom, t man] concern;

Be. it known that I, HERMAN A. AFREL, residing at Brooklyn, in the county of Kings and State of New York, have inyented certain Improvements in Multiplex Signaling Systems, of which the following is a specification.

This invention relates to high frequency multiplex signaling systems, and especially to an arrangement for separating the 'signaling/.channels or groups of` such channels transmitted over the same transmission line, and amplifying tq varying degrees the currents of the said channels by means of a'pluwill be see-n that the foregoing method of rality of amplifiers differing in their amplification constants. v

In arrangements designed to amplify a Wide rangebf frequencies transmitted over a long wire circuit it is desirable to employ means to control the degree of amplification of the Various frequencies, so that the relatively'low frequencies which `are attenuated lessrin transmission over the circuit are not disproportionately increased in amount'by excessive amplification. I-Ieretofore this has been effected by an arrangement known as an attenuation equalizer which comprised a selective network connected between the. line and the input side of the amplifying element which introduced a loss in the circuit that in a general way bore a complementary relation to the loss introduced by the transmission line itself; that is, at the high frequencies a lowloss is introduced and at tht lo-w frequencies a high loss is introduced.

The combined attenuation of the line and the equalizer'is roughly a constant, independent of the frequency, therefore ywhen it is used vwith a repeater element such as2^ a1' vacuum tube repeater whose gain also is? substantially independent of the frequency, approximately equal V current will be obtained at the outpu'tside vof the repeater for all frequencies within the desired range. It

equalizing the-attenuation of a plurality of frequencies results in the introduction' of a loss by the selective network resulting from the artificial attenuation of thel lower fre-` quencies and in consequence thereof therep'eating element mustbe of such capacity 1920. Serial No. 383,941.`

ranging the amplifying ele-ments that the same e ements may be used in different combinations depending upon the frequenciestfo be amplified. f

Other and further objects of this invention will be apparent from the following description when read inconnection with the attached drawings of which Figure 1 shows an attenuation equalizing arrangement which embodies the basic principle Of. thisv invention, and Figure. la showsl schematically the method of using an attenuation' equalizer such as is shown 1n Figure 1 with a radio antenna, and Figures 2 andB show specific applications of the invention.

' In Figure l, L1 vrepresents Ialine overv which may be transmitted currents ranging in frequency,vfor example, from 0 to 50,000,

cycles. This, line is bridged across vthe iuput side of the attenuation equalizer, being connected directly With the band filter BF1 and the low pass filter LPF, connected in series. The output side of the band` filter BF1 is connected by means of transformer" 'Il Awith the amplifying element ,Ar Tlie output side of the amplifier A1, is connected by means of the transformer 'l2 with the input side of/ the band filters BF2 and BF3 connected serially;l In like manner the output side of the hand filter BFS is connected by means of the trans former T3 with an amplifier A2,.the output side of which is 4con-- nected by means of the transformer T4 with the input sidoI of the band filters BF4 and connected serially. Similarly the band filter BIF5 is connected with the amplifier A3, which in turn is connected with the band filters BF6 and-,BF7 and the latter filter,

BF7, is in turn connected with the amplifier A4 the output side of which is connected 'with the bandffilter BFS. The output side of the attenuation equalizer is connected with the line L2. The filtcrs'LPF1 and BF1 v villustrated and in .parallel if desired. The

filters LPF1 and BF1 are designed for example to separate the impressed currents into two groups having ranges from 0 to 10,000 mia from 10,000 to 50,000 cycles respectively. Vhen a plurality of currents havinga frequency range of from0 to 50,000 cycles are impressed across'the input side of the equalizer, currents ranging in frequency between 0 toA 10,000 cycles will pass to the output side of the equalizer through the filter LPF which is adapted to transmit this range of frequencies with negligible attenuation and will be impressed upon the line L. without amplification. Currents of the frequencies between 10,000 and 50,000 cycles will not pass through filter LPF, due to its high attenuating characteristics at thesefrequencies but will pass through the band filter BF1 and be impressed by the transformer T1 upon the amplifier A1. The currents as amplified lwill then be impressed by the transformer T2 across the band filters BFzand BFaconnected serially. Since the band filter BF, is designed to transmit therethrough currents having frequencies within the range tif 10,000 to 20,000 cycles, such currents will pass to the output side vof the equalizer without amplification; but

currents of higher frequencies ranging from .20,000 to 50,000 cycles will pass through the band filter BF3 and be impressed by the transformer T3 upon the amplifier A2. The amplified currents of these frequencies will be impressed by. the transformer T4 upon the filters BF4 and BF` connected serially.

a Since the filter BF4 is adapted to transmit a band of frequencies between 20,000 and 30,000 cycles the currents of these frequencies will pass therethrough and will be impressed upon the line L2 without further amplification. Those currents lying within the range of 30,000 to 50,000 cycles will pass through the band'lter BF5 and be impressed -upon the amplifier A3 by a transformer T5. The currents 'thus amplified will be impressed lby the 'transformer T6 upon the band filters BF, and BF1 connected serially. Currents .p lying within 'the range of 30,000 to 40,000 cycles will pass through the filtergBF6 and without further amplification will be impressed upon the line L2. Currents having ka yrange oi 40,000

to 50,000 cycles will pass through -the filter BF 7 and be impressed by thel transformer -the selected frequencies.

The arrangement shown in Figure 1 which is designed to effect the substantially uniform amplification of currents of a plurality of frequencies, discloses novel means adapted to select from a common transmission system different hands of frequencies siqierimposed 011 the said system, to pass lunamplifiedthe band or bands of frequencies requiring no amplification and to. amplify to various degrees by a process of selection and amplification the'remaining bands ot' frequencies.

lt will be seen that no amplification is given to the band containing the lowest frequencies, which are least attenuated by the line impedance, that the minimum vamount of amplification is given to the band next f higher in the frequency scale, and that the amount of amplification increases. with rise in frequency, so that the band of highestv frequencies, which are most-attenuated by lineumpedance, receives the maximum amphfication. In such an arrangement, the

ramplifiers need supply only the required amount of energy to each-band of fre.

quencies necessary to counteract the loss that each particular band of frequencies has suffered due to line impedance.

Another feature of this invention lies in the novel arrangement of the selecting elements and the amplifying elements whereby the amplification of all the bands of frequencies is effected by a single group of amplifying elements in tandem formation instead of 'by single amplifiers or groups of amplifiers designated and intended toserve only a particular channel or band of frequencies. Thus in the. arrangement shown inFigure 1, the band of ten to twenty thousand cycles receives one stage of amplification; the band of twenty to thirty thousand cycles receives two stages; thirty to forty thousand cycles, three stages and forty to fifty thousand cycles, four sta es, making a total of ten stages of ampli cation which is performed by four amplifier elements.

Although the drawing shows an arrange-` ment adapted for one-way operation only, 1t 1s to be understood that such arrangement may readily be connected into the well known twenty-two or twenty-one repeater circuit by means of which the arrangement vis adapted for two-way operation. Furthermore, .it is to be understood that the frevwith the circuit containing the attenuation equalizer and the receiving apparatus. The winding 4 is connected by conductors 5 with an attenuation equali/Zerwhich may be of any of the types illustrated or described herein. The attenuation equalizer 6 is connected by means of, conductors `7 with receiving apparatus 8, which may be'of` any well-known type. In the operation of this circuit, oscillations of thel frequencies or the; bands of frequencies to'which the antenna is responsive, will be impressed by the transformer 3 upon the attenuation equalizer, and the currents of the various component frequencies will be separated and amplified to certain predetermined degrees, depending upon .the degree"l of attenuation tovvhich the said frequencies were subjected in transmission to the antenna l; The resultant currents of the various component frequencies will be combined andiimpressed by the conductors 7 upon the receiving apparatus 8.` l In Figure L1 and^ L2y represent two transmission lines extending, forexample, east and west yrespectively from the repeater station X shown in the drawing. ,Let it be assumed for purposes of illustration that. over the lines L1 and L, there are being transmitted a plurality of telegraph channels ranging between 4,000 and 8,000 cycles and two channels 'for telephonectransmisson ranging between v8,000 and '15,000 cycles from east to 'west i. e. fronihL2 to L1 and two telephone channels ranging /from ,17 ,000

to 25,000 cycles from west to east, i. e. from Ll to L2. The line L1 is bridged across one sideiof the repeater circuit and-the line L2 across the other side of the said circuit, the said circuit comprising three branches, A,

. B' and C. Connected in branch A of the repeater circuit are band filters BF1 and BF2V which are' adapted to transmit a rangey of frequencies for example between 17,000 and 25,000 cycle-s, and an amplifier A,L which may0 be of any well known type adapted to -transmit currents in the direction sho-wn by the arrowi/ Similarly connected in .branch B of the repeater circuit are the band filters BF3 and BF4 designed to transmity frequencies within the range for example of 8,000 to 15,000 cycles and an amplifier A, designed to .transmit currents inthe direcg tionshownby the arrow. A- third branch C ofthe repeater circuit contains the band' filterBF5 whichis adapted to transmlt frequencies ranging between 4,000 and 8,000 cycles.' This branch contains no amplifier since it is `not desirable to amplify this low range of frequencies. In view of -thelfact that the range of frequencies in branch A is relatively higher than the frequencies in' branch B the said amplifier A1 shall provide two stages of amplification, whereas the amplifier A2 shall bebut a single stage Currents lying within the range of 4,000 to 8,000 cycles transmitted either east or west. over the lines L1 and L2 will pass through the branch C of the repeater ir- S0 cuit containing the band filter BF, without amplification. Such currents will not, ofcourse,q pass into the branches A and B, since the band filters are so designed as to sharplv attenuate frequencies outside the range desired to pass through these branches. Currents having a frequency rangeuof 8,000 to15,000 cycles transmitted over the line L2 to the line L1 will pass through the band filter BF3 to the input side of the amplifier A2 which, as stated l'may be a single stage amplifier. The amplified currents `willvpass through the filter BF4 and thence to the line' L1. Similarly-the bands of `frequencies embraced within the range of 17,000 to 25,000 cycles transmitted over the line L1 to the line-L2 will pass through' the bandfilter BF1 and be impressed upon the'two stageamplifier'Al, which may be y so operated as to give to each band of frequencies the proper degree of amplification dependent upon the degree of attenuation of the particular frequencies. Thus, for example, we may insert for the amplifier` v A1 an arrangement embodying the principle 10" set forth in Figure 1 whereby the lovvrI frequencies within the transmitted range f would receivev slight amplification and the higher frequencies greater amplification.

In Fig. 3 L1 and L2 represent two trans- 110 misskion lines over which currents ,ofpa plurality of frequencies may be transmitted inl each direction, the said currents lying within two ranges of vfrequencies hereafter' referred to as the low frequency and the high 'frequency currentsl or oscillations. Bridgc'd acrossnthe line 'L1 are the low frequency circuit 1 and the high frequency circuit 2; The low frequency circuit 1 has associated therewith a 'low' pass filter LF, 120 adapted to transmit readily 4currents within a given range of relatively lowfrequencies and `adapted to attenuate sharply' currents of what may be termed the high frequency i group. Also associated` with the circuitf.12J 1 is a triple Winding transformer T1 with which are connected the low pass filter LF,V adapted to balance the filter LF1 and a network o'r artificial line N1, adapted to balance the line L,

for lowfrequenciefs. The trans- 139i former T, is of the well known conjugate type, in which oscillations set up in the circuit 3 will produce no disturbance in the circuit 4 and Vice versa, so long as the line L1 and its associated apparatus is balanced by the network N1 and its associated apparatus. The low frequenpy circuits 3 and 4 arey connected with the inputl and the output sidesof the `amplifiers A, and A2, respectively.

i vThe high frequency circuit 2 has associated therewith a high pass filterV HFI, designed; to transmit readily oscillations of the high frequency group, and to attenuate 'sharply oscillations of the low7 frequency group. `The high frequency circuit 10 is connected with two of the windings of the triple winding transformer T3, which is of the same general type as the transformer T1. Bridged across the midpoints of the said two windings of the transformer T3, is the input side 5 of the translating circuit, having associated therewith high pass filters HFM HF4 and HF5 of the same generaltype as i the filter HFl, and also the amplifying units A, and A2. The outputcside of the translating circuit is connected with the third winding of the triple winding transformen T3V Bridged across the translating circuit are the low frequency output and input circuits 6 and 7, which are connected with the windings of thetransformer T2 similar to transformer T1. The transmission line L2 has associated therewith a lcw freformer T1.

quency circuit Sand a high frequency circuit 9. Associatedwith'the circuit 8 is the low pass filter LF3 and LF4 corresponding to LF 1 andrLF2 and the network' N2 is designed to balance the line L2 for low frequencies. Associated with the high frequency circuit 9 isy a high pass filter HF2, similar to HF1.

low frequency currents will Ibe impressed on the circuit 3 and in turn,'will be impressed by the transformer T4, upon the input side of the amplifier Ai. These low frequency currents will be amplified thereby and the amplified currents fiow through circuit 6,

' transformer T2, ,low pass filter LF,l into the circuit 8 and willbe impressed upon the Line L2 at thej point Y.' The high pass filter HF, prevents these amplified low fre- `4tant point thereon,.

former T5 upon ranges of frequencies.

q uency currents from passing into high frequency circuit 11. Currents of lowfrequency transmitted over the line L2 from a diswill be impressed upon the low frequency circuit 8 at the point Y. Passing -through the low pass filter LF3, `these low frequency currents"will enter the circuit 7 and will be impressed by the transthe amplifier A2, and, as

amplified, will be transmitted by the circuit 4 to the windings of the transformer Tl and will pass through the low pass filter LF1 and the circuit 1 to the line L1 at the point X. The low frequency currents amplified by amplifier A2 are prevented from passing to the amplifier A1 by the high pass filter HF4. This filter serves to keep the oppositely travelling low frequency currents in their separate paths, thereby preventing interference.

1t will be apparent from the foregoing description thatthe currents within the low frequency range pass through a translating circuit which is in effect a two-way, two-unit circuit, the amplification in one direction being that given by the amplifier A1 and in the other direction that given by the amplifier A2. 4

Currents within the high frequency range transmitted over the line L1, will pass into the circuit 2 and through the high pass filter li"1 into the high frequency circuit 10. Tiese high ffrequency currents vwill be impressed upon the translating circuit 5 and passing through the high pass filter HF3 will be impressed upon the input side of the amplifier'A2. The amplifiedw currents will then pass through the high pass filter HF4 and be again amplified'by the amplifier A1. The high frequency current from the output side ofthis amplifier, passing through the high pass filter HF5 will-be impressed by the transformer T3 upon the highr frequency outputcircuit and will pass to thefline L2. In a similar manner oscillations of the high frequency group transmitted from a remote point of the lineL2 will be impressed upon' the circ'uit 9 and passing through the high pass filter HF2 will be impressed' by the circuit 11 upon the windings of the transformer TB. These high tions will be amplified by passing through the amplifiers A, andAl, and the amplified high frequency oscillations resulting therefrom will finally be impressed upon the line L1 at the point from the foregoing de-J lll) frequency oscillatranslating circuit but adapted to the high frequency oscillati'ns to a the drawing is designed to be located at a point in a transmission circuit where the lines in each direction have substantially the same characteristics and are of a such length that little or no terminal reiection losses manifest themselves at the repeating point forl` the higher frequencies. It will be noticed, therefore, that the lines L,L and L2 are not balanced b artificial lines or networks for the high requency transmission. By using a common translating circuit in which the amplifiers are connected in tandem aproportionally greater amplification may be obtained at the higher frequencies where the attenuation is relatively large. It will also be apparent that the separation-between the two groups of frequencies may be accomplished by properly designed filters and -by a parallel connection of the filter cir` cuits .as shown in the drawing. These filters are of the well known type disclosed in the patents to George A. Campbell, 1,227,113 and 1,227 ,1.14, issued/May 22, 1917, which are designed to have high impedance outside their transmission range,ii1 order that little or no loss may be introduced into the adJacent frequency range.

Although the invention is shown embodied in a -form in which the low frequency oscillations are amplified by a 22 type of circuit and the high frequency oscillations by a 21 type of circuit, it is obvious that a reversed arrangement may readily beeifected by changing the high frequency filters and the low frequency filters into low and high frequency filters respectively and by adapting the networks N1 'and lT2 to balance their respective lines for high frequency currents.

Although this invention has been described and illustrated in connection with a a multiplex system/'over wire lines, it is not limited to such use-but may beused in any AI nultiplex system involving a broad range of frequencies, such as, for example, in radio system. Where the amplifying arrangement is Aintended to constitute a radio repeating station, the two sides of the repeating arrangement' withwhich in the drawings thelines L1 and L2 are connected, would be connected directly with the antenna circuitsl of the radio system, and where the amplifyi ing arrangement is to be employed as a repeater between a radio and a wire system, one of the sides of the amplifying arrangement would be connected with the antenna circuit and the other side with the wire line.

It will, of course, be understood that ali' though this invention has been disclose-,das

embodied in certain specific forms, that it, is capable of embodiment otherand different forms without departing from the scope of the appended c aims. c

What is 'claimed is:- a

1f In a multil'ex Signaling system, the

each method of equalizing the transmission of a plurality of frequencies transmitted by a common transmitting medium which confsists in separating the currents of different frequencies into individual circuits amplifying the current of each of said circuits to a. degree depending upon the degree of attenuation of' the current of the said 'circuit caused by transmission through the medium and combining the resulting currents.

2. In a multiplex signaling system, the method of equalizing the 'transmission of a plurality 'of channels of different frequencies transmitted by a common transmitting medium which consists in separating the ldifferent channels into individual circuits amplifying the currents of each of said circuits to varying degrees depending upon the .degree of attenuation of the current of the respective channel caused by ,transmission through the medium and combiningltthe resultin currents..`

3. n al multiplextransmission system, the combination with a transmission medium adapted to transmit a plurality of bands, of

frequencies of a repeater -having means to select and means to amplify each'band to a degree depending upon its attenuation durlduring transmission lover said medium, and

a second transmission means upon which all of the amplified frequencies are impressed. 5. In a multiplex transmission system adapted for the simultaneous transmission of aplurality of bands of frequencies, the combination with means for transmitting a plurality of bands offrequencies with different degrees of attenuation of a repeater having means to select and means to amplify a'nd to a .degree approximately inversely proportional to the efficiency of transmission of the said band and means to combine the amplified bands of frequencies. 6. In, a multiplex transmission -system adapted for the simultaneous transmission` of a plurality of frequencies, the combination with means for transmitting a plurality of bands of frequencies with ldifferent de- 'grees of attenuation of a'repeater having meansto select and meansfto amplify eachy of said frequencies to a degree approximately inversely proportional to the efiiciency of transmission of the said frequencies and means to combine .the amplified frequencies.

7. In a multiplex transmission system adapted for thesimultaneous transmissienv I of' a plurality ofibands of frequencies, the

coi'iibiiiation with transmitting means of a repeater comprising a plurality of selecting circuits and amplifying units individual to certain of said selecting circuits and combined in other of said selecting circuits.

8. In a multiplex transmission system adapted for the simultaneous transmission of a plurality of bands of frequencies, the combination with means for transmitting a -plurality of bandsof frequencies, of a icpeater coiiiprising a plurality of amplifying units arranged in tandem formation,- and a plurality of selective output circuits each responsive to a definite band of fieqiiencies and connected with the group of amplifying units in such way that the number of stages of amplification is dependent upon the relative position of the band in the frequency spectrum.

i). In a multiplex transmission system adapted for the simultaneous transmission of a plurality of bands of frequencies, the combination with transmitting means of a repeater comprising` a plurality of amplifying units arranged in tandem formation in an amplifying circuit, means for impressing a plurality vof frequencies upon the input side of said amplifying circuit and means individual to the. output circuit of each of said amplifying units to separate out the respective frequencies after they have received the required degree of amplification.

10. In a signaling system the combination circuit interposed between twoV sections of said transmission circuit and having -means 7' to amplify to different degreesoscillations leo of different groups of frequencies.

11. In a highfrequency signaling system, the combination with a transmission circuit carrying a .plurality of frequencies of a translating circuit interposed between sections of the said transmission circuit, comprising means to amplify/tto 'different degrees each of the said frequencies, `and frequency selecting means to separate the various amplified frequencies and to impress them upon the said transmission circuit.

1Q. In a high frequency signaling system, the combination with a transmission line adapted to transmit a plurality of groups of frequencies, of a repeater circuit situated approximately* midway electrically between the ends of the said line embracing a xtwo way two path amplifying circuit having artificial lines associated therewith to balance lsaid transmission line withrespect to one group of frequencies and a two way one path amplifying circuitdesigned to be balanced with respect tothe other group lof frequencies by the lines themselves the amplifying units being common to both amplifying circuits, and means associated with with a transmission circuit of a. translatingeach of said amplifying circuits to select oscillations of the proper frequency for each respective circuit.

' In a telephone repeater circuit, the combination of a two way two path circuit adapted to amplify oscillations of one group of frequencies, a two way one path circuit adapted to amplify oscillations of al second group of frequencies anda plurality of aniplifying elements common to both circuits, one half of the said elements being connected in each path of the said two path circuit and all of said elements being oo nneeted in tandem in the said one path circuit whereby a higher degree of amplifica tion is obtained in said one path circuit than in said two path circuit.

14.` In a telephone repeater circuit, the combination of means for impressing thereon a plurality of plurality of amplifying circuits each adapted to amplify the oscillations embraced within one group of frequencies, means associated with each amplifying circuit to select the oscillations of thegroup which the said circuit is designed to amplify and means to combine the amplified oscillations.

15. In a multiplex transmissionsystem, the combination with a radio frequency transmission means of a repeater, means to limpress radio frequency oscillations uponA the said repeater', the said repeater having means to select and means to amplify to different degrees the impressed oscillations of different frequencies, cuit arranged to have all of the amplified oscillations impressed thereon.

16. In an attenuation equalizer, the combination with a group of amplifiers in tandemformation of a group of filters each interposed between successive amplifiers, and all adjusted to narrow the band of vfrequencies that may be transmitted through the group of amplifiers.

17. In an attenuation equalizer, the combination with a group of amplifiers in tanodem formation of a group of filters each interposed between successive amplifiers and adjusted to narrow the band of frequencies' that may be transmitted through the group of amplifiers, and a second group of filters each of which has its input side connected groups of frequencies, ay

and a transmission cirn with the input side of a filter of the Said tion with transmitting means of a group of group andis so adjusted as to impress upon amplifiers, a group o filters each of W ich the said transmitting means the frequency 10 is lnter osed between successive amplifiers or frequencies not transmitted by the correand adJusted to narrow the band vof frespending filter-'of the said first group. quencies transmitted through successive In testimony-whereof, I have signed my amplifiers, and a second group of filters each name to this specification this 21st day of of which has its input side oonnected'with May 1920. v i the input 'side' of a filter of the said first HERMAN A. AFFEL. 

